Study on the solid thermal insulation mechanisms of nitrogen-doped graphene aerogels by molecular dynamics simulations and experiments

Abstract

Reduced graphene oxide aerogels (rGO aerogels) may become the next generation of thermal insulation materials. In this paper, the solid thermal insulation mechanisms of nitrogen-doped graphene aerogels (NDGA, rGO aerogels) were studied using nonequilibrium molecular dynamics simulations and experiments. The solid thermal resistance of NDGA is composed of the thermal resistance in graphene and the interfacial thermal resistance. Since the grain size of graphene in NDGA is much smaller than the phonon mean free path and the graphene sheet size, the defects and grafting play much more significant roles in lowering the thermal conductivity of graphene compared to sheet size. Vacancy defects show higher efficiency in lowering the thermal conductivity. Co-grafting and pyrrolic N addition further decrease the thermal conductivity. The interfacial thermal resistance of overlapped graphene is significant. It decreases with the increase of connection number. Bridging prevents the overlap of graphene, suppressing the heat transfer through overlap position. The thermal resistance in graphene plays a more significant role in the solid thermal insulation of NDGA compared to the interfacial thermal resistance. Overall, these findings provide a more thorough understanding of the solid thermal insulation mechanisms of NDGA. They are significant for the optimization and application of the aerogels.